There are multiple way to create the child record wheneevr the parent record created or updated. You can create this process using :-
1. Process Builder 2. Flow Builder 3. Apex Trigger
As you know, the process builder is going to retire soon from salesforce , so I recommend you to go with the flow builder.
You can create the simple record trigger flow on the respective object and in that drag a create an record action and update all the required field as below.
There are multiple way to create the child record wheneevr the parent record created or updated. You can create this process using :-
1. Process Builder
2. Flow Builder
3. Apex Trigger
As you know, the process builder is going to retire soon from salesforce , so I recommend you to go with the flow builder.
You can create the simple record trigger flow on the respective object and in that drag a create an record action and update all the required field as below.
You can refer this example :- https://developer.salesforce.com/forums/?id=9062I000000gDn5QAE
Also refer this youtube video :-https://www.youtube.com/watch?v=pgimn2RnYv0
Let me know if you find anything difficult, I will help you there.
Kindly mark it as the best answer if it works for you.
Thanks & Regards,
Priya Ranjan